1. Field of the Invention
This invention relates to preparation of polyalkyl hydroxyaromatics from polyalkylenes and hydroxyaromatics. More particularly, this invention relates to production of polyalkylphenols such as polybutylphenol, from the reaction of polyalkylenes such as polybutylene with hydroxyaromatics such as phenol, in the presence of an acid catalyst and an organic solvent having a boiling point range of from at about or below the boiling point of the hydroxyaromatic to at about or above the boiling point of alkylhydroxyaromatic by-products of the reaction.
2. Description of Related Art
Polyalkyl hydroxyaromatics may be prepared by alkylating hydroxyaromatics with polymeric olefins in the presence of acidic catalysts. During such a process, some extent of depolymerization is typical, leading to the production of undesirable alkylhydroxyaromatics. For example, tert-butylphenol is an undesirable alkylphenol by-product which typically occurs during polybutene alkylation of phenol. In a typical polybutylene alkylation process, excess amounts of phenol are commonly employed to ensure good yields of polybutylphenol product. Unreacted phenol is then typically separated from polybutylphenol product and recycled to the alkylation reactor. In conventional alkylation processes, tert-butyl phenol is typically present in the phenol recycle stream. Consequently, tert-butylphenol tends to build up in the alkylation reactor, resulting in reduced yield of polybutylphenol. To maintain tert-butyl phenol content at an acceptable level within an alkylation reactor (for example less than about 2% by weight), separation is typically required. Separation of tert-butylphenol from the alkylation process stream typically requires additional process steps, costs and necessitates system downtime. Depending on the method of separation employed, substantial amounts of phenol reactant may be lost and waste product containing tert-butylphenol generated and disposed of. For example, removal of tert-butylphenol from phenol is typically accomplished by fractional distillation.
A number of processes have been developed in an attempt to address depolymerization during alkylation reactions. Such processes utilize specific catalysts and/or alkylene polymers having specific structural characteristics selected to result in reduced production of alkylhydroxyaromatics such as tert-butylphenol. However, these processes typically do not eliminate depolymerization and/or may result in reduced yields of polyalkyl hydroxyaromatic product. Furthermore, these processes may restrict catalyst selection and/or require use of specific polymer compounds having certain chemical structures.
In a typical alkylation process, excess amount of a hydroxyaromatic reactant is commonly employed to ensure good yields of polyalkyl hydroxyaromatic product. For example, in a process for alkylating phenol with polybutylene, excess phenol is typically employed. Following reaction, unreacted phenol is typically separated from the polybutylphenol product and recycled to the alkylation reactor. In a conventional process, tert-butylphenol by-product is typically present in the unreacted phenol recycle stream. Consequently, tert-butyl phenol tends to build up in the alkylation reactor, resulting in reduced yield of polybutylphenol. Because increased concentration of alkylhydroxyaromatic in the alkylation reactor results in decreased polyalkyl hydroxyaromatic yield, it is typically necessary to remove alkyl hydroxyaromatics, such as tertbutylphenol from an alkylation system on a periodic basis. Removal of alkylphenol is typically accomplished by high temperature stripping. The necessity of removing alkylphenols from an alkylation reaction system increases cost and results in down time.
In addition to the above concerns, polyalkyl hydroxyaromatic products from conventional alkylation processes are typically relatively viscous liquids that may be difficult to pump and transport.